It has been revealed by the British astronomer Patrick Moore that, on the morning of January 4th 2014, an extraordinary astronomical event will occur. At exactly 9:47 am, the planet Pluto will pass directly behind Jupiter, in relation to the Earth. This rare alignment will mean that the combined gravitational force of the two planets would exert a stronger tidal pull, temporarily counteracting the Earth’s own gravity and making people weigh less. Moore calls this the Jovian-Plutonian Gravitational Effect.

Moore told scientists that they could experience the phenomenon by jumping in the air at the precise moment the alignment occurred. If they do so, he promised, they would experience a strange floating sensation.

Astronomers have long been aware that there would be an alignment of the planets on that date, when Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto would be on the same side of the Sun, within an arc 95 degrees wide. But now the effect could be expected as the gravitational effect of the other planets on the Earth’s crust is maximum even at their closest approach.

If you think you will be able to float around your house then you will be mistaken. BUT if you jump in the air at 9:47AM local time on January 4th 2014, it should take you about 3 seconds to land back on your feet instead of the usual 0.2 seconds.

January 4th 2013 will be a popular day for crazy stunts going on youtube. Do you have any ideas for stunts?

The Jovian–Plutonian gravitational effect, a hoax phenomenon stated to cause a noticeable short-term reduction in gravity on Earth, was an invention for April Fools' Day by the EnglishastronomerPatrick Moore broadcast on BBC Radio 2 on 1 April 1976.
...
On April 1, 1976, Moore stated to radio listeners that an astronomical event would take place at 9:47 a.m. that day, a conjunction of Jupiter and Pluto, which was expected to have an effect observable everywhere. As Pluto passed behind Jupiter, it would briefly cause a powerful combination of the two planets' gravitation which would noticeably decrease gravity on Earth. If listeners were to jump into the air at that exact moment, they would find they felt a floating sensation.[5][6]

Soon after 9:47 on that morning, the BBC began to receive hundreds of telephone calls from people reporting they had observed the decrease in gravity.[5] One woman who called in even stated that she and eleven friends had been sitting and had been "wafted from their chairs and orbited gently around the room".[7]

[Added by Mick:]
The simplest debunk of this is to note that the Moon is the only planetary body that produces observable gravitational effects (the tides), and that those effects are not noticeable when jumping up and down (you feel the same weight at high tide and low tide). Jupiter and Pluto have no effect on the tides, and so must have an effect that is much less than the moon.

Hence the alignment of Jupiter and Pluto must have at most an effect that is twice something that is much less than the moon, which is not noticeable. So this effect will not be noticeable itself.

One could also do the math, which is more complicated, but not incredibly so.

Compare that with Earth gravity, g = 9.8 m/s^2, Jupiter has an effect of 0.0000037% of normal earth gravity. So with Jupiter at its closest a 200 pound person would feel 0.0000074 pounds lighter.

Pluto being aligned with that will simply add a very tiny, but basically negligible, amount to that, because Pluto is a very small body (about 1/100000th the mass of Jupiter), and is much further away than Jupiter. I leave it as an exercise to the reader to calculate how much acceleration Pluto will add at its closest point. But it's significantly less than Jupiter, and hence basically nothing.

It was definitely Kurt Vonnegut, I think it was "Hocus Pocus", the Chinese learned to control gravity. Everybody knew they were doing it because every male got a hard on. I'll let you know on the 5th if gravity was affected.

A 37 year-old joke being recycled. Quite amazing, and it speaks to the longevity of hoaxes, urban legends, and conspiracy theories. If you've not seen it before, then it's new to you, so there's always a fresh batch of people to run the joke on.

Astronomers have long been aware that there would be an alignment of the planets on that date, when Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto would be on the same side of the Sun, within an arc 95 degrees wide. But now the effect could be expected as the gravitational effect of the other planets on the Earth’s crust is maximum even at their closest approach.

... is lifted directly from the Wiki entry for Gribbin's Jupiter Effect. The second sentence has been changed from "But no effect could be expected as the gravitational effect of the other planets on the Earth's crust is minimal even at their closest approach."